Vehicle signalling apparatus

ABSTRACT

This device for giving and controlling a vehicle U-turn signal comprises a U-turn signal indicator (1) and a control circuit. The U-turn signal indicator (1) can consist of an array of LEDs which makes a loop circuit with an arrow. One can be mounted on the front plate (2) of a vehicle, and another one can be mounted on the back plate. The control circuit consists of a rectifier, a first integrator, a second integrator, a counter, a switching transistor, and a relay. The output of the rectifier is connected to the inputs of the first and second integrators of which the outputs are connected to the CLK and to the RST of the counter respectively. The outputs of the counter and the rectifier are connected to the inputs of the NAND which controls the on or off working state of the switching transistor and the relay, to activate the U-turn indicator. The input of the rectifier is connected to the turn signal pulses of a vehicle. When certain pulse patterns are generated, the U-turn signal indicator is activated.

This invention relates to apparatus for giving and controlling vehiclesignals, such as vehicle U-turn signals.

Most vehicles are equipped generally with turn signals commonly referredto as left and right turn indicators. Using such turn signals toindicate the intention of a driver to make a U-turn is inconvenient inoperation and ambiguous in meaning, which can result in an increase inthe frequency of accidents.

The invention seeks to mitigate problems such as this.

According to the invention there is provided a vehicle signalling systemcomprising a main indicator, an activating device, a timing device formeasuring the intervals during which the activating device is notactivated and means responsive to the activating device and to thetiming device to activate the main indicator when the measured intervalis less than a threshold value.

With fewer parts, eliminating extra switches, brackets, and redundantactivation operations, apparatus embodying the invention can use theon-off-on wording state of an existing turn signal as the input.

The U-turn indicator may comprise an array of LEDs which makes a loopcircuit with an arrow.

The invention will further be described by way of example with referenceto the accompanying drawings, in which:

FIG. 1 is a control circuit diagram of apparatus embodying theinvention;

FIGS. 2a-2g are wave forms of the control circuit of FIG. 1;

FIG. 3 is a schematic illustration of a first U-turn indicator for usein apparatus embodying the invention; and

FIG. 4 is a schematic illustration of a second U-turn indicator for usein apparatus embodying the invention.

In this embodiment the turn display comprises a plurality of LEDs 1,activated by a battery B1 through normally open contacts for a relay.The relay coil is activated by a battery B2 through a switchingtransistor 8550.

The vehicle has a turn indicator control (not shown) which causes atrain of pulses to be supplied through a rectifier consisting of diodesD1 and D2 in series and a resistor RS return to earth. The pulse trainis applied through respective diodes D4 and D5 to integrators I1 (C1 R1)and I2 (C2 R2), the time constant of I1 being less than that of I2. Theoutput of I1 is applied through two inverters N2 and N3 in series to theclock input of a counter UL; the output of the integrator I2 is appliedthrough a single inverter N1 to the reset input of the counter UL. Thecounter has outputs Q1, Q2, Q3 etc., and the outputs Q2 and Q3 areapplied to respective inputs of a NOR gate through an inverter N4 to oneinput of a NAND. The rectified pulse train is applied directly to theother input of the NAND, whose output is connected to the base ofswitching transistor 8550 through a resister R4.

The effect of this circuit is that the NAND gates the rectified pulsetrain being applied to the switching transistor 8550 according to thestate of the counter UL. FIG. 2 shows waveforms at different points inthe circuit. Waveform (a) shows a first pulse train of two pulsesfollowed by a short delay, less than 3 seconds, followed by a secondpulse train of four pulses, followed by a long delay. When the pulsetrain starts, the rectified pulses charge up the integrators, whoseoutputs are then high. When the train stops, the outputs decay accordingto their time constants (waveforms (b) and (c)), so that after a firsttime the clock input will be changed from high to low (waveform (d)) andafter a second longer time the reset input will be changed from low tohigh (waveform (e)) provided that no further pulse train has started.The outputs start to decay after the pulse train stops, so theintegrators are measuring the time during which the twin indicatorcontrol is not activated. When a second pulse train starts theintegrators will again charge up.

Considering first the case where the second train starts after bothintegrator outputs have dropped to the level which causes their outputinverter to change state, as shown at the right hand ends of thewaveforms, the reset input of the counter will have been activated andso the counter will be at zero. The following pulse train generated whenthe turn indicator is activated again will therefore be treated inexactly the same way as the first pulse train.

Considering now the case where the second pulse train starts after thefirst integrator has dropped to change the state of its inverter, butbefore the second integrator has changed the state of its inverters, asat the left hand end of the waveforms, the reset input of the counterwill not have been activated (waveform (e) remains low) and the counterwill retain its count of one. When the second train arrives, thecharging up of the first integrator will cause the counter to increaseits count to two and the consequent output on Q2 (waveform (f)) willactivate the NOR gate and enable the NAND which is gating the rectifiedpulse train being applied to the switching transistor. The switchingtransistor and the relay are thus energised by the gated pulse train(waveform (g)) and the U-turn indicator activated. The indicatorcontinues to be activated until the pulse train stops, and 3 secondslater the second integrator output decays sufficiently to reset thecounter, thus disabling the NAND. If the turn indicator control isactivated again before the 3 second elapses counter UL will advance itscount to 3 and the NAND gate will remain enabled and the U-turnindicator will be re-activated.

A further activation of the turn indicator control within 3 seconds willnot keep the NAND gate enabled because there is no connection from theQ4 output of the counter UL to the inverter N4.

In this embodiment, the time constant of the second integrator isselected so that the waveform (e) goes high 3 seconds after the pulsetrain stops provided another train has not started. 3 secondscorresponds to the time between the end of the right hand pulse inwaveform (a) and the rise of waveform (e). The time between the end ofthe first pulse train and the start of the second is less than 3 secondsand so waveform (e) continues to remain low.

As a practical matter, the driver should wait at least 3 seconds afteractivating the U-turn indicator (by activating the turn indicatorcontrol twice in quick succession) before activating the turn indicatorcontrol again, in order to allow the U-turn indicator to be reset.

The connection of Q2 and Q3 to respective inputs of NOR gate preventsnoise from the turn signal triggering the U-turn indicator falsely,since such noise may cause the counter to advance its count by one otherthan as a result of the signals from the integrators I1 and I2.

As shown in FIG. 3, a hollow rectangle array of LEDs 1 (the U-turnindicator) is placed in a transparent plastic loop set and mounted onthe rear plate 2 of the vehicle. The sides of the rectangle embrace thelicence plate.

An arrow head 4 is incorporated pointing downward on the left hand sideof the indicator. A similar indicator can be mounted on the front plateof the vehicle with its arrow head pointing downward on the right side.

FIG. 4 illustrates another way by which a brake indicator 3 is combinedwith the U-turn indicator 1, both of them being mounted on the backinside window of a vehicle. In this case, the brake indicator 3 and theU-turn indicator 1 are in different flashing colours. For example, thebrake indicator is in red, while the U-turn indicator is in amber-green.

The LEDs of the U-turn indicator can all be energised together orfurther switching means can be incorporated so that groups of LFDs areenergised sequentially with the pulses of the train. The groups can beof different colours, or at different locations such as the oppositesides of the display.

What is claimed is:
 1. A vehicle signalling system comprising a mainindicator, an activating device, a timing device for measuring theintervals during which the activating device is not activated and meansresponsive to the activating device and to the timing device to activatethe main indicator when the measured interval is less than a thresholdvalue.
 2. A system is claimed in claim 1, wherein a second indicatoractivating means is arranged to respond to the activating device aftereach of a limited number of successive intervals less than the thresholdvalue.
 3. A system as claimed in claim 2, comprising a furtherindicator, and means responsive to any activation of the activatingdevice to energise the further indicator.
 4. A system according to anyone of claims 1 to 3, wherein the timing device includes a plus counter.5. A system according to claim 4, wherein the means responsive to thetiming device includes a switching transistor and a relay.
 6. A systemaccording to claims 5, wherein the activating device is adapted tocontrol operation of the turn indicators of the vehicle.
 7. A systemaccording to claim 6, wherein the main indicator is adapted to indicatethe performance of a U-turn.
 8. A system according to claim 7, whereinthe U-turn indicator comprises a plurality of LEDs.
 9. A systemaccording to claim 8, the main indicator being adapted for mounting forviewing through a window of the vehicle.
 10. A system according to claim9, wherein the main indicator includes an arrow head.
 11. A systemaccording to claim 8, the main indicator being disposed in a licenceplate of the vehicle.
 12. A system according to claim 6, wherein theLEDs are arranged to form substantially a U-shape.
 13. A systemaccording to claim 7, wherein the control circuit is adapted to energisethe LEDs sequentially, from one arm of the U, to the other.